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Modeling and Real-Time Simulation of Internal Faults in Synchronous Generators With Parallel-Connected Windings
Abstract
In large synchronous generators, the stator windings are usually parallel-connected in order to increase the machine current capacity. In analysis and modeling, the parallel windings are usually lumped into one equivalent stator winding since equal currents flow in these windings. However, when an internal fault occurs in the windings, the symmetry between the parallel windings is broken and different currents will flow in the parallel windings since unsymmetrical magnetic linkage may exist between the stator windings. The aim of this paper is to present a simulation model to investigate the internal fault currents of large synchronous generators with parallel-connected windings. This model is based on a modified winding function theory that takes into account all space harmonics. Moreover, the calculation of the machine inductances is made easier by the use of the machine electrical parameters instead of the geometrical ones. The simulation results illustrate the existence of different currents in parallel windings in the case of internal faults. Results are given for an implementation of the internal fault model in a real-time simulator of large power networks
... A cost-effective fault model is especially useful for large-power electrical machines because performing fault tests on them is costly, difficult and often destructive. For these reasons, some prior work on ITSC fault modelling of different electrical machines has been carried out by researchers [10][11][12][19][20][21][22][23][24][25]. In the literature, there are three well-established methods to model ITSC faults, i.e., the analytical approach, magnetic equivalent circuit, and finite element method (FEM). ...
... Therefore, it is desirable to develop a relatively simple general analytical fault model that can use either analytical or FE inductance parameters. However, it has been reported in [10,19,20] that a system with a large number of first-order differential equations is required to characterize the fault model when loop or branch currents are used as state variables, which makes the ITSC fault modelling of large-power electrical machines very challenging. Therefore, it would be very useful if the fault model could be simplified. ...
... It is often convenient to use an analytical approach to calculate inductances at an initial design stage when the winding configuration of the studied machine is not complex. Unlike the large-power synchronous machines in [20], large-power SPM wind generators often have a simple winding configuration. In this paper, the distributed single-layer winding with a slot/pole/phase (SPP) equal to 1 has been used for the fault modelling, as shown in Figure 2. Equations (1)-(3) clearly show that the number of first-order differential equations to characterize the fault model using branch currents as state variables is determined by the number of parallel branches. ...
This paper proposes a general analytical model for large-power surface-mounted permanent magnet (SPM) wind generators under inter-turn short-circuit (ITSC) faults. In the model, branch currents rather than phase currents are used as state variables to describe the electromagnetic behavior of the faulty machine. In addition, it is found that the multiphase Clarke transformation can be used to simplify the proposed fault model with the inductances calculated analytically or numerically using finite element analysis. With the latter, both linear and nonlinear inductances can be obtained, and the non-linear inductances are used for the fault modelling of large power rating machines due to larger electrical loading and heavier magnetic saturation. With the developed fault model, studies of scaling effects (different power ratings such as 3 kW, 500 kW and 3 MW) and the influence of fault location on the electromagnetic performance of SPM generators with series-parallel coil connections have been carried out. The simulation results show that large-power SPM wind generators are vulnerable to ITSC faults when a relatively small number of turns are short-circuited and a single-turn short-circuit fault at the top of the slot is found to be the worst case.
... However, for medium and large-power electrical machines, such as the ones used in wind power, series-parallel coil connections are often used to increase the phase current whilst reducing the phase voltage level, and the models based on series-connected and parallel-connected coils might no longer be applicable. In [12][13][14], the transient behaviour of salientpole synchronous machines with series-parallel coil connections under internal faults including ITSC fault was modelled using branch currents as state variables due to unequal branch currents when an internal fault happens. However, the cumbersome inductance calculation considering the practical distributed winding arrangement and large-scale systems of differential equations required to characterise the fault model make ITSC fault modelling for large salient-pole synchronous generators quite complex and challenging. ...
... However, the cumbersome inductance calculation considering the practical distributed winding arrangement and large-scale systems of differential equations required to characterise the fault model make ITSC fault modelling for large salient-pole synchronous generators quite complex and challenging. In addition, the fault models proposed in [12][13][14] are not really general and simple, and they cannot provide much meaningful physical insights into the fault performance. ...
... Different from the developed fault models in [12][13][14][15][16], this paper proposes a general and relatively simple analytical fault model in a concise block matrix form for SPM machines with series-parallel coil connections using branch currents as state variables. In the fault model, the mutual inductive coupling between any two branches has been considered. ...
A general analytical model is developed in a concise block matrix form for surface‐mounted permanent magnet (SPM) machines with series‐parallel coil connections under inter‐turn short circuit (ITSC) fault. In the model, branch currents are used as state variables and inductances of different series‐parallel coil connections are calculated using an analytical method, namely winding function approach (WFA) together with slot permeance method. Based on the characteristics of the calculated inductances and the developed fault model, the multiphase Clarke transformation has been proposed to simplify the fault model. In the process of model simplification, the healthy machine model using branch currents as state variables have been proven to be equivalent to that using 3‐phase currents as state variables. The proposed fault models of a 3kW 96‐slot 32‐pole SPM machine with different series‐parallel coil connections have been built in Matlab/Simulink and validated by time‐stepping 2D FE simulations. Simulation results show that different series‐parallel coil connections have little influence on the amplitude of the ITSC current. Finally, a small scale 24‐slot 8‐pole SPM machine prototype has been built to further validate the accuracy of the proposed fault model.
... The fault simulation can be generalized for only the machines of the same make and size with identical stator winding arrangement. The MWFA has been used to simulate different types of internal and external faults using machine electrical parameters instead of the geometrical ones [10]. The inductances are derived directly from the original waveforms using turns function of the actual machine winding distribution; hence the space harmonics are taken into account. ...
... The co-efficients K 0 and K 2 are the machine geometrical constants and can be represented by the machine electrical parameters L md and L mq as expressed in equation (5) The internal faults in the stator winding do not affect the winding distribution of the rotor windings, however due to change in the winding distribution of the faulted windings of the stator, the mutual inductances between the rotor and the stator should be calculated. The mutual inductance between an arbitrary stator winding x and and the damper windings kd, kq are given as [10] ...
... The synchronous machine modeling during an internal fault can be done with the help of (18-23). The elements of the inductance matrix can be calculated for salient-pole machines using (4-6, 16-17) and non-salient pole machines (10,(14)(15)(16)(17). ...
This paper presents the application of neural networks for the non-differential protection of salient-pole synchronous generator against internal faults in any winding of the stator. The direct phase quantities and modified winding function approach has been used to simulate different types of internal and external faults using electrical parameters of generators installed by utilities. The cases of all the possible types of internal faults in the stator winding have been taken into consideration in designing the protection scheme. Multi-layer Feed-forward Neural Network (MFNN) and Radial Basis Function Neural Network (RBFNN) have been trained and tested for detection, identification and classification of the internal faults based on pattern classification. The simulated fault currents in the phases as well as their parallel paths at the terminal end have been used for training and testing of both the proposed neural networks. Both the networks are able to identify the fault signal correctly but the MFNN is more reliable, more accurate and faster than RBFNN in detection and classification of the fault.
... For physics-based modelling of permanent magnet (PM) machines under ITSC fault, there are three major methods in literature: (1) winding function approach (WFA) [6], [7], [8], [9], [10], (2) finite element (FE) approach [11], [12], [13], and (3) magnetic equivalent circuit (MEC) approach [14], [15]. WFA is a circuit-based modelling method in essence, and it is the foundation of analytical derivation and calculation of inductances of integer-slot AC machines [16]. ...
... WFA is a circuit-based modelling method in essence, and it is the foundation of analytical derivation and calculation of inductances of integer-slot AC machines [16]. Researchers in [6], [17] have tried to use this method to analyze the fault performance of induction and synchronous machines in the last 30 years. The disadvantage of this method for calculating the inductances is that it neglects the core saturation and also space harmonics. ...
This paper proposes a general analytical model of surface-mounted permanent magnet (SPM) machines with series-connected coils under inter-turn short circuit (ITSC) fault. One prominent feature of this fault model is that the air-gap and slot-leakage components of inductances under fault are calculated separately, and the influences of pole number and spatial distribution of coils have been considered in the calculations. In the model, the winding function approach (WFA) is used to calculate the air-gap inductance components by considering all space harmonics whilst slot-leakage inductance components are obtained by using slot permeance method. The proposed fault model built in Matlab/Simulink is validated by time stepping FE simulations for a 3kW 96-slot 32-pole SPM machine. The fault model has acceptable accuracy and is suitable for the fast evaluation of fault performance of SPM machines and its accuracy considering core saturation can be improved using FE-based results. Other power ratings (0.5MW and 3MW) have also been investigated to study the scaling effect on machine fault-tolerant capability. A 12-slot 4-pole small scale prototype has been built to validate the developed fault models.
... It is then developed by H.R.Akbari [35] to model the rotor misalignment in each axially-divided cross section for calculating the inductance under the axial non-uniformity conditions considering the rotor skewing and several rotor asymmetries. It is also adopted by Tian et al. [36] to identify the characteristics of stator current under composite faults of broken bar and static eccentricity in a squirrel cage IM. Tu et al. [36] apply it in a large synchronous generator with parallel connected windings for the real-time simulation of the internal faults. ...
... It is also adopted by Tian et al. [36] to identify the characteristics of stator current under composite faults of broken bar and static eccentricity in a squirrel cage IM. Tu et al. [36] apply it in a large synchronous generator with parallel connected windings for the real-time simulation of the internal faults. Magnetic saturation effect is often neglected in this method, but it can be taken into account by introducing the saturation factor along a particular region of the air-gap circumference in a saturated IM [28] or in a salient-pole synchronous generator [37]. ...
The requirement for a more compact solution in electrical machines leads to a design trend of increasing rotational speeds and lightening mechanical structures. These changes can lead to non-linear vibrations and even to the rotor-stator contact in the worst case. These vibrational phenomena are mainly generated by the unbalanced magnetic pull (UMP) inside the machine due to the air gap eccentricity. In order to study the influence of different architectures on these complex vibrational phenomena, a multiphysics electrical machine model with strong electro-magnetic-mechanical couplings is developed in this thesis. The different interaction paths between the UMP force and the radial displacements of the rotor have been introduced to fully strengthen this coupling considered on both radial and rotational movements. The proposed model is established on the basis of the angular approach so that an originality of this work lies in the fine understanding of the instantaneous angular velocity (or angle-time relationship) of the motor shaft. This originality also provides the formalism and the framework to solve the problems in the non-stationary operating conditions. The mixed mesh/nodal permeance network is also adopted to model the deformed magnetic field under the effect of the rotor eccentricity and the mass eccentricity. This multiphysics model is validated by comparing with a more classical finite element model in the quasi-static regime. Two traditional electric motor architectures (the squirrel cage induction motor and the permanent magnet synchronous motor) are chosen as examples of the application of the proposed model. The physical characteristics of the UMP force and its frequency components associated with the input static eccentricity are studied in the case of the induction motor. Then, the self-excited vibration of the rotor is analyzed through the UMP waveform and the radial displacements of the rotor center in the case of a permanent magnet synchronous motor architecture. The resonance peak generated at the modified natural frequency by the mass unbalance excitation is also identified from the two results. The two models are finally used respectively to study the influence of different mechanical structures and the effect of different winding configurations.
... However, that is applicable to the concentrated winding or sinusoidal air gap field. In order to accurately calculate the inductance parameter of the short-circuit winding, the winding function theory (WFT) is employed to model the internal faults of synchronous machines [2,[9][10][11]. According to the actual windings distribution, the inductances are directly calculated by using the geometrical and electrical parameters of synchronous generators. Moreover, all the space harmonics in the air gap are included in the calculation of winding inductances. ...
... It is needed to note that if α = 0, i.e. the axes of coil AA′ and coil BB′ coincide with each other; the mutual inductance will become the self-inductance. Generally, for calculating the inductances according to formula (9), taking only two items will satisfy the precision demand. ...
Fractional pole‐ratio winding is a new type of AC winding, consisting of coils with different pitches. The application of fractional pole‐path ratio windings in synchronous generators will bring new problems to the modelling and simulation of internal faults. It is important to establish a mathematical model for the fractional pole‐path ratio synchronous generators with internal faults and accurately calculate the fault currents. In this study, the multi‐loop model of fractional pole‐path ratio synchronous generators is first proposed. The method for calculating mutual inductances between stator coils with arbitrary pitch is given, and all the space harmonics, including the fractional ones, are considered in the inductance calculation. In order to improve the simulation accuracy of turn‐to‐turn faults, the effect of core localised saturation is modelled by modifying the air gap function of fault coils. A 300 MW fractional pole‐path ratio synchronous generator is set as an example, and three types of internal faults are simulated. The comparisons of simulation results are made between the multi‐loop model and the finite element model to verify the validity of the multi‐loop model proposed in this study.
... Validation is made with an OPAL-RT simulator [21]. Using a refined synchronous machine model [22], which is incorporated into OPAL-RT's Hypersim, several fault and non-fault conditions are investigated. ...
... The N parallel windings of one phase are spatially distributed around the stator. Their position is used to compute the winding functions necessary for the self and mutual inductance parameters [22]. ...
... Validation is made with an OPAL-RT simulator [21]. Using a refined synchronous machine model [22], which is incorporated into OPAL-RT's Hypersim, several fault and non-fault conditions are investigated. ...
... The N parallel windings of one phase are spatially distributed around the stator. Their position is used to compute the winding functions necessary for the self and mutual inductance parameters [22]. ...
This work presents an analytical methodology for synchronous generators stator faults protection. The proposed method is built on a differential protection relay strategy. A morphological filter is applied on the differential current providing real-time signal characterization. Unlike the traditional percentage differential relay, the proposed analytical methodology is able to detect all types of stator faults, including those close to the neutral end, which generates small differential currents due to the high impedance grounding of generator. Validation is done with OPAL-RT using a phase-domain synchronous machine model, which represents realistic operating conditions. The results of test cases highlights the method's dependability and security. Easy to implement models without hard-to-design parameters indicates the method’s potential for real-life applications.
... The success of the technique depends not only on its ability to distinguish between healthy and faulty states but also on its ability to discriminate between various faults. Many diagnostic techniques for induction machines can be extended easily to other types of electrical machines [8][9][10][11]. ...
... In fact, short circuit current saturates locally and strongly the magnetic circuit of the machine. In the case of PNM based model, this phenomenon causes the apparition in the stator current spectrum of new harmonics representing the saturation effect which the corresponding frequencies are given by relation (11). Figure 9 shows the simulation results of stator currents for healthy and faulty cases. ...
This paper presents an accurate and reasonably complicated model to simulate the faulty induction machines. The proposed model is based on a Permeance Network Method (PNM) coupled to the differential equation system governing the induction machine behavior in presence of stator faults. The proposed model allows taking into account the local magnetic saturation due to the relatively high fault current with moderate simulation time compared to the finite element method (FEM). Simulation results illustrating the impact of saturation in the case of some common stator faults such as stator inter-turn short circuits, shorted phase and open phase faults are presented and their comparison with those issued from coupled magnetic circuit based model proof the pertinence of the proposed approach. Experimental results validate the PNM approach in modeling saturated machines. The presented simulation results demonstrate the necessity to survey multiple quantities in order to distinguish between different fault signatures and in so doing to diagnose the type of a stator fault.
... WFA is a circuit-based modelling method in essence, and it is the foundation of analytical derivation and calculation of inductances of integer-slot AC machines [4]. Some researchers in [5], [6] have tried to use this method to analyze fault performance of induction and synchronous machines in the last 30 years. The disadvantage of this method for calculating the inductances is that it neglects the core saturation and also space harmonics. ...
... It should be noted that the effectiveness of TSC as a mitigation solution is dependent on several factors, such as the machine type [8,11], winding connection scheme [13,14], and fault location within a slot and phase coils [5,15]. In general for surface-mounted PM machines, the PM field is strong and the residual flux linkage after TSC may still be too large. ...
Effective mitigation of excessive stator turn fault current is crucial for fault tolerant machine drives. In this paper, a simple and effective method is proposed for a triple redundant 3x3-phase permanent magnet assisted synchronous reluctance machine (PMA SynRM) by using 3-phase 4-leg inverters. The fourth leg creates a zero sequence current path when a terminal short circuit (TSC) is applied in an event of a turn fault in a 3-phase winding set. Consequently, the zero sequence flux linkages are reduced by the resultant zero sequence current. This leads to lower residual flux linkage and decreased fault current. The machine drive can therefore have larger safety margin or can be designed for improved torque density and efficiency. The proposed approach is verified by both FE simulations and experimental tests in a wide operation range. It shows the fault current is reduced by ~40% and the output torque is not affected.
... However, this is acceptable when the windings are concentrated or a pure sinusoidal distribution of magnetomotive force exists in the air gap. Another synchronous machine model, which is presented in [10][11][12][13][14][15][16], analyzes the internal faults based on the modified winding function theory by the electrical parameters of the machine. Although all space harmonics generated by the windings are accounted by this model, the assumption of sinusoidal distribution cannot justify the large salient pole synchronous generators. ...
In this paper, a novel method is presented for detection and classification of the faulty
phase/region in the stator winding of synchronous generators on the basis of the resulting harmonic components that appear in the terminal voltage waveforms. Analytical results obtained through Decision Tree (DT) show that the internal faults are not only detectable but also they can be classified and the related region can be estimated. Therefore, this scheme can be used to protect the synchronous generators against the various internal faults. Fuji technical documents and data sheets for an actual salient pole synchronous generator (one unit of an Iran’s hydroelectric power plants) are used for the
modeling. Simulations in Maxwell software environment are presented. All the related parameters, such as B-H curve, unsymmetrical air gap and pole saliency, slot-teeth effect, and other actual parameters, are considered to obtain a comprehensive model to generate acceptable terminal voltage waveforms without any simplification.
... After that, many researchers have introduced nonlinear approaches to determine UMF in the last two decades. For instance, winding function analysis [10], conformal mapping method [11], energy conservation law [12], magnetic equivalent circuit method [13] and exact subdomain model [14] were all applied to investigate the magnetic field distribution and UMF for electrical machines with non-uniform air-gaps. The most commonly adopted analytical method is the air-gap permeance approach [15,16]. ...
Electrical machines are important devices that convert electric energy into mechanical work and are widely used in industry and people’s life. Undesired vibrations are harmful to their safe operation. Reviews from the viewpoint of fault diagnosis have been conducted, while summaries from the perspective of dynamics is rare. This review provides systematic research outlines of this field, which can help a majority of scholars grasp the ongoing progress and conduct further investigations. This review mainly generalizes publications in the past decades about the dynamics and vibration of electrical machines. First the sources of electromagnetic vibration in electrical machines are presented, which include mechanical and electromagnetic factors. Different types of air gap eccentricity are introduced and modeled. The analytical methods and numerical methods for calculating the electromagnetic force are summarized and explained in detail. The exact subdomain analysis, magnetic equivalent circuit, Maxwell stress tensor, winding function approach, conformal mapping method, virtual work principle and finite element analysis are presented. The effects of magnetic saturation, slot and pole combination and load are discussed. Then typical characteristics of electromagnetic vibration are illustrated. Finally, the experimental studies are summarized and the authors give their thoughts about the research trends.
... • Some internal-fault models have been developed specifically for integration into real-time digital simulators [17] [18] [19]. Numerical efficiency is given a higher priority in these formulations. ...
Stator winding interturn, interbranch, and series faults can result in large circulating currents in the faulted coils. Generator protection elements may not be sensitive enough to detect these fault conditions until the fault evolves into a phase-to-phase or phase-to-ground fault. Large machines have been severely damaged by delayed or failed protection system operation. Determining fault quantities for the various possible internal faults is not trivial and requires the aid of numerical models. Protection element models can then be used to determine the protection coverage provided by these elements.
Certain machine modeling methods are useful for analyzing external faults or power system transients but are not appropriate for analyzing internal faults. The most commonly used machine models use dq0 transformation and assume an ideal equivalent model of the machine derived from its normal operating mode using lumped winding parameters. Consequently, these models ignore the effect of the strong harmonics that result from the internal machine asymmetry during internal faults. Alternate methods, such as symmetrical component analysis or phase-coordinate methods, are simplified models that introduce large errors during internal asymmetric conditions.
The multi-loop method treats a machine as a set of loops in relative motion. The method involves a permeance analysis of the machine to calculate the time-variant electric parameters of the stator branches and rotor loops. The stator branches (including fault branches) are converted to loops via a transformation matrix corresponding to the state of the machine. The model is then solved using a numerical method. Because the multi-loop method uses machine geometry and winding design information, it preserves the harmonics that result from internal faults. The transformation matrix provides a simple and intuitive mechanism to apply internal faults in the fractional winding.
In this paper, we validate the multi-loop method using test data from a scale-model machine in a lab. We then use the fault quantities obtained from the multi-loop method to determine the sensitivity and coverage provided by various generator internal-fault protection algorithms for the lab machine.
... After that, many researchers have introduced nonlinear approaches to determine UMP in the last two decades. For instance, winding function analysis [16], conformal mapping method [17], energy conservation law [18], magnetic equivalent circuit method [19] and exact subdomain model [20] were applied to investigate the magnetic field distribution and UMP for electrical machines with non-uniform air-gap. The most commonly adopted analytical method is the air-gap permeance approach [21,22]. ...
... It provides a synthetic definition of machine inductances able to capture their dependency on rotor position. However, referring to [13]- [16], a small air-gap width is a necessary condition for the WFT to provide accurate results. The drawback of this method is the requirement of design data such as number of slots and winding structure. ...
... It provides a synthetic definition of machine inductances able to capture their dependency on rotor position. However, referring to [13]- [16] a small air-gap width is a necessary condition for the WFT to provide accurate results. The drawback of this method is the requirement of design data such as number of slots and winding structure. ...
This paper proposes an original, simple and fast permanent magnet synchronous generator model, implemented with a new conception on the graphic interface of Matlab/Simulink environment. The obtained physical model suggests a new way to easily carry out different types of stator faults such as inter-turns short circuit faults, phase to phase faults and phase to ground faults as well as simultaneous multi-faults. This is handled by connecting the two desired points in the stator, on the graphic interface of Simulink, exactly as they can be carried out in the experimental tests. This model has the originality to take into account the arrangement of the stator windings of a multi-pole machine by differentiating between the windings under the same pole-pair and those under different pole-pairs. A comparison between the simulated and the experimental results is done to verify the behavior of the proposed model in both healthy and faulty modes under different operating speeds. The good comparison results lead to validate the correct behavior of the proposed model with a satisfactory accuracy.
... However, this can be acceptable when the windings are concentrated or a pure sinusoidal distribution of magneto motive force (MMF) exists in the air gap. A synchronous machine model has been presented in [10][11][12][13][14][15][16] to analyze internal faults based on the modified winding function theory using machine electrical parameters. Although all space harmonics generated by the windings were accounted by this model, assumption of sinusoidal distribution is not realistic for large salient pole synchronous generators. ...
In this paper, a novel method is presented to detect and classify turn-turn faults (TTF) in stator winding of the synchronous generators on the basis of resulting harmonics contents in the terminal voltage waveforms. Analytical results by using Decision Tree (DT) show that this algorithm is practicable using only the first harmonic of residual voltage and only two harmonic component values. Simulations in Maxwell software are done using Fuji's technical documents and data sheets of an actual salient pole synchronous generator (one unit of an Iran's hydroelectric power plants) and all of related parameters (such as B-H curve, unsymmetrical air gap and pole saliency, slot-teeth effect, and so on) are considered to obtain a comprehensive model, without any simplifier assumption.
... Real-time simulators are a complementary tool to conventional offline simulation programs for power system studies [20], [21]. With much more computational power, real-time simulators are able to simulate very complex and large models in real-time or faster [22], [23]. In recent years, RTS has been applied for many system studies; however, applications in the power quality area, particularly for harmonic analyses of a high-voltage system, are rarely found and are limited to small test systems [24], [25]. ...
... Real-time simulators are a complementary tool to conventional offline simulation programs for power system studies [20], [21]. With much more computational power, real-time simulators are able to simulate very complex and large models in real-time or faster [22], [23]. In recent years, RTS has been applied for many system studies; however, applications in the power quality area, particularly for harmonic analyses of a high-voltage system, are rarely found and are limited to small test systems [24], [25]. ...
Nowadays in high-power industrial processes, multipulse cycloconverters are the most commonly used converter for high power mill drives. This paper propose an analysis of the interharmonics currents behavior under an unbalanced load, injected by a Cycloconverters (CCVs) with 12- pulse configuration and multi-winding transformers. Three-phase transformers with two secondary windings with star and delta connection and a three-phase RL load with a decoupled direct current load control are used to simulate the system. The prototype of the power system is embedded on a real-time simulator. Performance is tested on a digital real-time power system simulation (RTDS) and results are analyzed with external equipment and compared with theory.
... As a basic tool, various reference-frame-theory-based applications are reported in the recent studies, like finding deviation in an actual Concordia pattern used to determine the types and magnitude of faults in drive systems and stator, respectively [28,29], obtaining negativesequence stator-fault-related indices from the line current [30], and detecting negative-frequency rotor asymmetry signatures at standstill based on complex fault signature vectors [31]. ...
Electrical machines are critical components in industrial processes. A motor failure may yield an unexpected interruption at the industrial plant, with consequences in costs, product quality, and safety. To determine the conditions of each part of motor, various testing and
monitoring methods have been developed. In this paper, a review on effective fault indicators and condition monitoring methods of rotating electrical machines has been accomplished. Fault detection methods divided to four groups: electrical, mechanical, chemical and thermal indicators. Some fault detection methods based on electrical
symptoms like stator current, voltage, their combination or spectrum discussed in electrical group. In second branch, mechanical symptoms like torque, vibration and so on used for condition monitoring. Third group, chemical indicators, assigned to some chemical parameters of materials like oil characteristic or wear and debris in oil analysis. In last group, thermal symptoms in rotating electrical machines will be spoken. Between all methods, some of them are more known like vibration and some of them are recently added like motor current signature analysis (MCSA). Nowadays, combined methods and methods used artificial intelligence (AI) in condition monitoring are more popular. In every group, the fault detection method and the faults that can be detected have been mentioned. Mathematical equations of some new signal processing method have been discussed in literature presented in appendix.
... Simulation-based approaches are commonly used in the industry to validate and test various systems. In Tu et al. (2007), simulation models are used to investigate internal fault current of large synchronous generator. Similar approaches allow to validate electromagnetic compatibility of electronic design before prototyping in Lai et al. (2006). ...
In this case study, we focus on improving the design flow of a Schneider Electric protection device, using modelling and simulation approaches at both the cycle accurate bit accurate (CABA), and the transaction (TLM) modelling levels. We therefore perform hardware/software design space exploration using virtual prototyping for this industrial device to meet its real-time constraints at a low hardware cost, while improving its reliability and robustness by using fault injection techniques. These approaches are demonstrated on a medium voltage protection relay called Sepam10 in order to define evolutions of its architecture that are further validated on an FPGA prototype. This example is considered to be typical of a wide class of protection and safety devices, thus showing that the modelling approaches used in high complexity system on chip (SoC) devices are also of great interest for power electronic board-based control devices.
Interturn short-circuit (ITSC) is one of the most common faults in permanent-magnet synchronous machines (PMSMs), and ITSCs in PMSMs with parallel-connected winding (PCW) are generally more difficult to detect than those in PMSMs with series-connected winding. In this article, the mathematical model of PCW PMSM with ITSC is established first, and the main fault features of ITSC such as the third harmonics in phase currents, negative sequence of phase voltages and circulating current are also modeled. Then, the reasons for the weak fault features in PMSMs with PCW are analyzed. Furthermore, the effects of ITSC modes, including single-branch ITSC and branch–branch ITSC, and short-circuit position on these fault features are investigated. It is shown that branch–branch ITSCs are more difficult to detect, especially when the short-circuit position is close to the midpoint of phase winding. Experimental tests are carried out on a PCW PMSM with ITSC, and the experimental results agree well with the theoretical analysis.
This paper presents a general analytical fault model in a compact matrix form for surface-mounted permanent magnet (SPM) machines with parallel-connected coils, which is useful to study the machine performance under the inter-turn short circuit (ITSC) fault. To simplify the fault model, the multiphase Clarke transformation has been proposed. In the model, the branch currents rather than the phase currents are employed as state variables to describe machine behaviours under fault. Additionally, self- and mutual-inductances are obtained by winding function approach (WFA) plus slot permeance method. The proposed analytical fault model is applied to a 3 kW 96-slot 32-pole SPM machine and validated by time-stepping FE simulations. A small scale 12-slot 4-pole SPM machine prototype has also been built to further validate the accuracy of the proposed fault model.
The finite element method provides a deep understanding of the magnetic behavior of electrical machines. Its use requires solving the Maxwell and Poisson equations in a combination of difficult boundary conditions related to the complicated geometry of the electrical machines. The winding function approach, or modified winding function method, is one of the most accurate and appropriate methods for synchronous generators (SGs). This chapter includes the magnetic saturation effect in the faulty salient‐pole SG. In this method variations of the air gap length instead of the variations of the permeability of the iron parts are considered. This can simply and precisely take into account the saturation effect in the air gap distribution function of the generator. The air gap function in the no‐load and on‐load conditions must be modified to consider the saturation factor in WF modeling.
The arrival of the energy transition to the global electricity scene has led to the implementation of new technologies in power systems and modified the way that the energy is generated, distributed and consumed. The analysis of the operation and the consequences of the inclusion of new technologies become a very important topic in the studies carried out by the utilities. Real-Time Digital Simulators (RTDS) have become a powerful modeling tool that allow to analyze power system models with a high level of fidelity, permitting to anticipate problems and the assessment of solution strategies. Due to the increase in the use of this technology and considering that there are no review articles on RTDS applications written in Spanish, this paper presents an explanation of the characteristics of RTDS along with an updated state of the art related to applications in Energy Transition as a theoretical framework with a large amount of information collected for future researches in Latin America.
Accurate stator turn fault (STF) modelling technique is of paramount importance to assess the machine fault behavior and develop fault detection and mitigation strategies for a fault tolerant machine drive system. In this paper, a STF model is proposed for a triple redundant 3x3-phase permanent magnet assisted synchronous reluctance machine (PMA SynRM). The effect of turn fault current is represented by equivalent inputs to a general flux linkage model for each 3-phase set. Subsequently, the flux linkage of the fault turns is derived according to the coil location and slot position of the fault. The complete model is obtained by combining the flux linkage model with the governing voltage equations. The effectiveness and flexibility of the proposed model have been validated by extensive finite element (FE) simulations and experimental tests in various operation conditions. It is demonstrated that the model can predict the machine behavior with and without the mitigation action in the form of terminal short circuit (TSC).
In the paper, a combined strategy of moth–flame optimization (MFO) algorithm and fuzzy logic controller (FLC) for incipient fault diagnosis of the synchronous generator is proposed. The motivation behind the proposed topology is to analyse the beginning issues exhibited by an asynchronous generator under different situations like healthy and unhealthy conditions. Initially, a synchronous generator is assessed in the ordinary condition and from that point onwards, fault is made in the synchronous generator and the framework practices are checked and signals are measured which can be viewed as mis-shaped waveforms. For the collection of data-set from the input current signal, MFO is presented which extracts the signal and structures the possible data-sets. In light of the fulfilled data-set, the FLC performs and diagnoses the kind of fault that has happened in the stator winding of the synchronous generator. In order to evaluate the effectiveness of the proposed method, the incipient faults are analysed. The proposed technique is implemented in MATLAB/Simulink platform and this is approved utilizing execution measures, for example, accuracy, precision, recall, and specificity. Likewise, the proposed method is analysed with factual measures, for example, the root mean square error, mean absolute percentage error, mean bias error, and consumption time; and the execution is evaluated by utilizing the examination at various strategies like artificial neural network, fuzzy, and adaptive neuro fuzzy inference system techniques.
The research of aircraft generator stator winding faults has great significance to the generator protection design, and the conclusion of the research can be further used to provide a reference for aircraft maintenance decision. In this paper, the inductance parameters of the aircraft generator were calculated at the beginning based on the air-gap permeance method. Then the aircraft generator model with and without stator winding internal fault were built according to the multi-loop method. As two typical fault scenarios of the aircraft generator, inter-turn short circuit and inter-phase short circuit were introduced into the simulation model. And the simulation results show that the excessive short line current has a significant impact on the performance of the motor, which proves that the protection device is necessary for the generator. In addition, the harmonic distribution of the fault current was compared with the case without fault injected, which leads to the observation that the stator current contained more odd harmonics, and the excitation current contained more even harmonics. What's more, such harmonic analysis can provide a theoretical basis for fault diagnosis research.
A precise simulation of the internal faults of synchronous generators is crucial for the design of the main protection scheme; therefore, an accurate model is necessary. In this paper, based on the circuit-coupled finite element method (CCFEM), an improved model of a synchronous generator with internal faults is proposed, wherein, the localized model of each stator coil is built as per its actual structure. Using this model, the internal fault occurring inside the coil can be accurately simulated, better approximating the location of the actual fault point; thus, the fault currents can be calculated more accurately. The accuracy of the improved model is verified by a dynamic simulation experiment. Moreover, the electromagnetic magnitudes, such as the air gap flux density, fault currents, field current, and all the damper currents are investigated in detail, under fault conditions, thereby, revealing the fault characteristics more clearly and providing a basis for designing protection schemes.
In this paper, artificial neural network (ANN) approach is used to detect two types of incipient faults viz. inter-turn insulation failure and bearing wear in single-phase induction motor. The experimental data for five input parameters viz. motor intake current, rotor speed, winding temperature, bearing temperature and the noise is generated in the laboratory on single phase induction motor. Initially the performance is tested with two inputs i.e. motor intake current, and rotor speed, later the remaining three input parameters were added step by step and in this way the four types of ANN based fault detection systems are designed. The training and testing results are given for all the four systems. It is found that the as the input parameters added sequentially, the accuracy of fault detection get improved.
All available techniques based on modified winding function approach, approximate the mean radius of the air-gap and simplify the geometrical model of salient pole machines. This approximation is applied in geometrical evaluation of this function and determining the inductances of salient pole machines. In this paper an improved MWFA is applied to calculate inductances of a salient pole synchronous machine under different eccentricity conditions. The improvement of the method is verified with FE analysis. Inductances with the improved MWFA are compared to those obtained from MWFA and it is shown that the results with the improved method are closer to those obtained from finite element computations. Effects of stator and rotor slots and several rotor asymmetries on inductances in these conditions are shown.
Power system stabilizer plays a vital role in a typical power system by improving the steady state stability margin and increasing the system positive damping thereby it enhances the stability of the system. Power system stabilizer can be designed to improve the dynamic stability of the power system and suppress the low frequency oscillations effectively. the importance of a PSS by analyzing a typical base case model with power system stabilizer and comparing the without a power system stabilizer. Apart from increasing steady state stability, use of Conventional power system stabilizer in power systems has drawbacks such as non-optimal damping and presence of noise ripples in power output. These drawbacks can be addressed by Model reference Adaptive controller (MRAC). Even though the stabilization time is less for CPSS compared to MRAC, the effect of low frequency oscillations reduction using MRAC takes precedence and is overshadowed by its drawbacks of high stabilization time. Lyapunov method is implemented while designing model reference adaptive control.
The turn-to-turn short circuit (TTSC) fault is one of the most common faults in Brushless Synchronous Generator (BLSG). The robust TTSC fault detection, diagnosis and protection techniques require better understanding of the BLSG behaviour during such conditions. This paper presents an improved mathematical model of the main generator in BLSG with TTSC on a stator phase windings. In the proposed BLSG model, the performance under high degree of TTSC fault is improved by combining the d-q model approach and Winding Function Approach (WFA). The d-q model approach is used to keep the model simple for the development of online model based condition monitoring, and the WFA is used to improve the accuracy of the model under TTSC fault condition. The WFA is also used to consider the saturation effect in the model to improve the model accuracy under high degree TTSC fault condition. The verification results showed that the developed BLSG model is able to provide accurate and consistence performance under wider range of TTSC fault in the stator windings.
In this paper, first, turn-to-turn fault in a synchronous machine stator winding is investigated, and its inductances are derived with the winding function method. Then, using the nonlinear control theory, the first-order Poincaré map of the synchronous machine is computed, and a new extended Poincaré map of the machine is established. Also, the characteristic multipliers of the synchronous machine are calculated by the Poincaré map. This new map is capable of analyzing electrical machines in the nonlinear and unbalanced cases for evaluation of stability, bifurcation, and chaos phenomena. The results show that the new map is an effective technique for modeling and analyzing any AC electrical machines. The characteristic multipliers and the Lyapunov exponents of the extended map indicate the system's condition. Chaotic phenomena are observed in some machines with internal faults. Since chaotic systems have a continuous spectrum and various kinds of frequencies in their spectrum, identification of the internal fault location is not easy with harmonic analyses such as Fourier spectrum method on the excitation current in synchronous machines. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
SUMMARY This paper presents a model for the analysis of internal faults of synchronous generators with multiple parallel connection paths for phase. Several kinds of faults between different portions of the stator windings (and ground, if the case) can be described in the subtransient time frame. Data necessary for the model derive from the electromagnetic design of the machine, as well as from details on equivalent parameters of the external grid and from the neutral connection characteristics. Such modeling procedure allows accurate insight of currents in windings and terminals, exploring each possible fault configuration. In the second part of this work, the developed model will be applied to assess the validity and to define possible improvements of conventional protection configurations against internal faults. Copyright © 2013 John Wiley & Sons, Ltd.
The task performed by induction motors grows increasingly complex in modern industry and hence improvements are sought in the field of fault diagnosis. It is essential to diagnose faults at their very inception, as unscheduled machine down time can upset critical dead lines and cause heavy financial losses. Artificial intelligence (AI) techniques have proved their ability in detection of incipient faults in electrical machines. This paper presents an application of AI techniques for the detection of inter-turn insulation and bearing wear faults in single-phase induction motors. The single-phase induction motor is considered a proto type model to create inter-turn insulation and bearing wear faults. The experimental data for motor intake current, rotor speed, stator winding temperature, bearing temperature and noise of the motor under running condition was generated in the laboratory. The different types of fault detectors were developed based upon three different AI techniques. The input parameters for these detectors were varied from two to five sequentially. The comparisons were made and the best fault detector was determined.
When an internal fault occurs in a synchronous generator, the symmetry between the parallel paths of the winding is broken and different currents flow in them, due to unsymmetrical magnetic linkage between the stator windings. The aim of this paper is to present a simulation model to investigate the effect of internal fault on the parallel path currents of a large synchronous generator using direct phase quantities. This model is based on a modified winding function approach where the machine inductances are calculated directly from the machine winding distribution using machine electrical parameters instead of the geometrical ones. The simulation results for different cases of internal faults in salient-pole and non-salient-pole synchronous machines have been obtained. Salient-pole synchronous generator has wave winding distribution while the non-salient-pole generator has lap winding arrangement. Due to different stator winding arrangements, the two machines have been simulated individually. By using the simulated fault data, a suitable numerical protection scheme for synchronous generators can be developed.
This paper presents the development and implementation of d-q axis components and wavelet packet transform (WPT) based hybrid technique for digital differential protection of salient pole synchronous generator. In this paper, the analysis is concentrated on the high frequency sub-band contents of WPT obtained from the d-q components of the differential currents of the relay. It has been found that the analysis in this approach provides information to detect any fault in the synchronous generator. This hybrid technique provides good accuracy and fast fault clearance with only one level of WPT of the d-q axis components of the current. Off-line results of the collected data from an experimental work are utilized for different cases of system disturbances.
In this paper, the development and implementation of d-q axis components and wavelet packet transform (WPT) based hybrid technique for digital differential protection of a salient pole synchronous generator is presented. The analysis is concentrated on the high frequency sub-band contents of WPT obtained from the d-q components of the differential currents of the relay. It has been found that the analysis in this approach provides enough information to detect any fault in the synchronous generator. This hybrid technique provides good accuracy and fast fault clearance with only one level of WPT of the d-q axis components of the current. Off-Line testing is carried out for the data collected from an experimental work on a laboratory salient pole synchronous generator for different types of disturbances. Moreover, the algorithm is verified by Real-Time experimental tests on the laboratory salient pole synchronous generator.
This paper presents real-time development, implementation and testing of a hybrid technique, based on d-q axis components and a wavelet packet transform (WPT), for differential protection of a salient pole synchronous generator. The high frequency sub-band contents of the d-q axis components of the output generated currents are analyzed using the WPT. It has been found that this analysis provides enough information to detect any fault in the synchronous generator. This hybrid technique provides good accuracy and fast fault clearance speed with only one level of WPT of the d-q components of the generated current. Real-time experimental test results are provided in this paper for different cases of disturbances on the output terminal of the salient pole synchronous generator.
In this paper a method for simulating an axial-flux induction machine with squirrel cage is presented. The Simulation is based on the multiple coupled circuit theory wherein the needed inductances are calculated with the winding function theory. This simulation model is the basis for fault simulations like short circuits. First, the principle arrangement and the machine data are shown. After a short introduction to the winding function and multiple circuit theory the calculation of the self- and mutual- inductances based on its Fourier series is explained. Moreover the difference between using a rectangular and a trapezoidal characteristic of the winding function is described. Especially for this type of machine the needed assumptions and simplifications are presented as well. In a next step the simulation model implemented in Matlab/Simulink is presented. The paper ends with some simulation results compared to the machine data and a short conclusion.
Recently, the capacity of turbo generators used in power plants is increasing in order to keep up with the growth of electric power consumption in the world. Turbo generators are consequently experiencing problems, including increasing electromagnetic force, temperature rise of armature coils, etc., as we try to increase the armature current to keep pace with the capacity increase. One way of avoiding these problems is to increase the number of parallel armature windings for decreasing the armature current per coil. However, the circulating current in the parallel windings is generated by the difference of the linkage flux of each winding, when the number of parallel windings is not a divisor of pole numbers. In this paper, we propose a simple method to calculate the circulating current by using a magnetic circuit in the design phase. We confirmed the proposed method has a similar accuracy and faster performance in comparison with the finite element method (FEM) analysis. And then we applied the proposed method to a calculation of the circulating current in 2- and 4-pole generators and considered the factors affecting the circulating current.
SUMMARY Different radial eccentricities in salient pole machine are well documented in previous studies. In reality, the most probable case is the rotor eccentricity, which is not uniform down the axial length. This article determines a precise model of salient pole synchronous machine for general axial eccentricity condition. Proposed model allows calculating salient pole machine inductances with different static, dynamic, and mixed axial eccentricities in a unified technique. By taking into account machine geometry, slots effects, and type of winding connection, this model is able to consider most of the important features of a salient pole machine. A variant of modified winding unction approach has been used to calculate the inductances under axial eccentricity conditions. The effects of several rotor asymmetries on the inductances are shown, and the inductances are evaluated. The evaluated inductances are compared with those obtained from experiments. There is a good agreement between the simulated and the experimental inductances profiles. Copyright © 2012 John Wiley & Sons, Ltd.
This paper demonstrates a multiplatform hardware-in-the-loop (HIL) approach to observe the operation of a high-speed permanent-magnet synchronous generator coupled with a microturbine in an all-electric-ship power system. The mathematical model of the gas turbine and the dynamic equations of the high-speed generator are implemented in real time on a field-programmable gate array (FPGA). This real-time simulation interfaces with hardware via a serial peripheral interface to a supervisory digital signal processor (DSP) of a three-phase voltage source inverter. The inverter output load is virtually emulated in the FPGA using received hardware measurements from the DSP. A user input interface is introduced using dSPACE on a personal computer to acquire data and adjust the speed reference of the generator system through a serial communication interface to the DSP. The real-time simulation and HIL experimental setup are validated in a scaled medium voltage dc ship power system.
This paper presents an investigation of the behavior of a 200-MVA-synchronous hydrogenerator during interturn stator faults, focusing on the affection to the electromagnetic magnitudes, such as the currents and the electromagnetic torque. Two kinds of interturn fault are examined 1) a short circuit between two conductors belonging to the same phase; and 2) a short circuit between two conductors belonging to different phases. These faults have been investigated via simulation using the finite element method. The benefit of this method is that it gives the possibility to calculate, except from the classical electrical magnitudes (e.g., the stator and field currents, the load angle, and the electromagnetic torque), other magnitudes which in general are difficult to compute during transient operation (e.g., the damper currents and the electromagnetic field inside the machine air gap). The main aim of this paper is to highlight quantitative and qualitative the condition in the interior of the machine in the cases of typical faults, which usually can occur during the machine operation. So, it is possible to find out that faults exist in the machine through the measurement of the field and the stator currents.
An analysis method is developed for modeling of multi phase cage
induction motors with asymmetry in the stator, arising due to an
interturn fault resulting in a disconnection of one or more coils making
up a portion of a stator phase winding and any distribution and number
of rotor bar and end-ring failures. The approach, based on the winding
functions, makes no assumption as to the necessity for sinusoidal MMF
and therefore include all the space harmonics in the machine. Simulation
and experimental results confirm the validity of the proposed method
The performance of multiphase machines designed for operation with
static power converters is investigated. The winding distributions are
intentionally rectangular to better accommodate the rectangular
waveforms of solid-state inverters. Equations which define the transient
as well as steady-state behavior, including the computation of all
machine inductances, are derived. In deriving these equations the space
harmonics are specifically included. Equations for calculation of
terminal voltages and electromagnetic torque are modified to account for
nonsinusoidal air-gap-flux distributions. A conventional three-phase
induction motor including the effect of space harmonics is simulated
A transient machine model of a doubly fed reluctance motor is derived by means of winding function and d-q transformation theory. The machine consists of a double wound stator having four and eight pole sets. The rotor is equipped with six poles. The machine, related to the Hunt motor, has a synchronous speed of a twelve pole machine. Comparison of simulated to tested results indicates that the higher harmonics in the motor inductances are important for predicting current waveform. KEYWORDS: Reluctance Motor, Hunt Motor, Electric Machine Modelling.
In this paper, the winding function method in conjunction with the
coupled magnetic circuit approach are used to develop the dynamic
equations of a five-phase synchronous reluctance machine in the natural
frame of reference (a-b-c-d-e). The effect of the third harmonic of the
airgap MMF is included in this development. A five-phase transformation
from the (a-b-c-d-e) system to a (d<sub>1</sub>-q<sub>1</sub>-d<sub>3
</sub>-q<sub>3</sub>-n) system is introduced. This transformation
removes the angular dependency of the inductances. Using this
transformation, equations for a five-phase synchronous reluctance
machine, including the third harmonic of the airgap MMF, were obtained.
The resulting equations are compared with the equations in the natural
(a-b-c-d-e) system. Simulation traces are used to confirm the validity
of the model. Finally, the developed equations are compared to
experimental results and their similarities and discrepancies are
identified
This paper extends the winding function theory for nonuniform air gap in rotating electric machinery. It shows that the winding function differs from that used in the symmetrical case, although several papers employ the uniform air-gap winding function to study electric motor performance under fault conditions. The extended theory will be particularly helpful in the study of squirrel-cage induction motors with a nonuniform air gap such as that caused by eccentricity of the rotor and stator.
Special winding connections used in certain dual voltage or multiple-speed single-phase motors lead to large, even order MMF harmonics, which must be included in calculations. The equations developed for two-phase machines are specialized to yield harmonic equivalent circuits for steady-state operation, and yield equivalent circuits representing actual machine windings. A numerical example of a machine operating with only its north poles excited is included.
Two unbalanced faults (line-to-neutral and line-to-line
short-circuits) in a synchronous machine are simulated by the finite
element method (FEM). In order to accomplish these tasks, the FEM had to
be associated with the moving-airband technique as well as the coupling
with electric circuit. Results obtained in the simulations concerning
the armature current and torque are compared with analytical
curves
An internal fault in the armature winding of a synchronous machine occurs at the breakdown of either the minor insulation (turn-to-turn fault) or the major insulation (phase-to-ground fault). The faulty synchronous machine is represented by an equivalent circuit in three symmetrical components which can be connected to the corresponding network. The fault currents can be calculated from the obtained equivalent network. The calculation of internal fault currents has been programmed for the IBM 7090 digital computer, and the calculated values have been compared with the experimental results.
This paper presents a model of a synchronous machine which is capable of representing internal faults in the windings. Since the topology of the circuit representing the machine is altered in the presence of such faults, the two-reaction theory and the resulting Park Transformation cannot be readily applied in these situations. The model presented is derived in the phase domain. The model takes into account the type of winding, and the geometry of the stator and the rotor. The accuracy of the model is validated by comparing the results with recorded waveforms.
This paper presents the effect of dynamic air-gap eccentricity on
the performance of a salient pole synchronous machine. The modified
winding function approach (MWFA) accounting for all space harmonics has
been used for the calculations of machine winding inductances. In
addition, the winding inductances have been calculated by the finite
element method to support those calculated by the MWFA. Relationships
between stator current induced harmonics and dynamic air-gap
eccentricity were investigated. The coupled magnetic circuits approach
has been used for modeling the synchronous machine performance under the
dynamic air-gap eccentricity. Finally, experimental results to
substantiate the theoretical findings are presented
The special winding connections used in certain dual voltage or multiple-speed single-phase induction motors lead to large, even order MMF harmonics. The calculation procedures used to evaluate machines of this type must include proper representation of these harmonics. This paper develops the general describing equations for a two-phase machine with arbitrary MMF distributions. These equations are then specialized to yield harmonic equivalent circuits for steady-state operation. Proper interconnection of these harmonic circuits yields equivalent circuits representing actual machine windings. Examples are given, including circuits for representation of consequent pole windings. A numerical example of a machine operating with only its north poles excited is also included.
Internal stator winding faults in salient-pole synchronous
machines can cause serious damage to a machine and the system to which
it is connected. Thus, it is highly desirable to be able to accurately
model their transient behaviour and to predict the resulting currents
and voltages in order to develop appropriate protection schemes,
particularly for high power machines. Based on the multi-loop circuit
method, a general mathematical model for a salient-pole synchronous
machine with internal faults is established, and subsequently employed
to simulate both the steady-state and transient behaviour for three
different types of internal fault. Predicted results are validated by
experimental measurements
Working group F-8 “Digital Simulator Performance
Requirements for Relay Testing” of the Relay Input Sources
Subcommittee, Power System Relaying Committee, was formed in 1992 with
the following assignment: “Investigate performance characteristics
of digital simulators when generating electromagnetic transient program
(EMTP) and digital fault recorder (DFR) based relay test waveforms.
Write performance requirements specifications and prepare a paper
describing the importance of the simulator performance
characteristics.” This paper presents the work accomplished by the
working group in fulfilling its assignment
This paper discusses the construction of a mathematical model of a
large synchronous machine suitable for analyzing internal phase and
ground faults in stator windings. The method employs a direct phase
representation, and uses conventional, and readily available, machine
data. The methodology was validated by comparison with results obtained
from independent finite element analyses
The paper describes a method for the dynamic simulation of dynamic
rotor eccentricity in squirrel cage rotor induction machines. The method
is based on a winding function approach, which allows for all harmonics
of magnetomotive force to be taken into account. It is demonstrated how
this complex dynamic regime can be modeled using the mutual inductance
curves of symmetrical machine using proper scaling techniques.
Experimental results demonstrate the effectiveness of the proposed
technique and validate the theoretical analysis
Standstill frequency-response (SSFR) literature to date has
primarily focused on turbo-alternators, which have a double-cylindrical
topology. Synchronous machines driven by hydraulic turbines or internal
combustion engines are salient-pole machines whose electrical constants
are somewhat different due to construction differences: (1) the
salient-pole topology produces a ratio of L<sub>q</sub>/L<sub>d</sub> of
approximately 0.5 as opposed to unity for cylindrical-rotor machines;
(2) the salient poles are constructed of steel-sheet stampings rather
than forged steel; (3) salient-pole field windings are concentric
whereas those of cylindrical rotor machines are distributed; (4)
salient-pole generators often have amortisseur windings embedded in the
pole faces; and (5) fractional slot/pole/phase (SPPP) stator windings
are commonly employed in salient-pole machines whereas turbo-alternators
are more apt to be limited to integral SPPP windings. These differences
alter time constants, inductances, and transfer functions. This paper
provides needed information for the modeling of salient-pole machines
for use in simulation studies using a theoretical approach
An internal fault in the armature winding of a synchronous
generator occurs due to the breakdown of the winding insulation. In this
paper, a method for simulating internal faults in synchronous
generators, using direct phase quantities, is described. Simulation
results showing the fault currents, during a single phase to ground
fault and a two phase to ground fault, are presented
A synchronous machine internal faults model based on the actual winding arrangement is described in this paper. Based on the winding function approach, the machine inductances are calculated directly from the machine winding distribution, thereby the space harmonics produced by the machine windings are readily taken into account. Moreover, the calculation of the machine inductances is made easier by the use of the machine electrical parameters instead of the geometrical ones. Simulation results for internal faults on a laboratory generator are compared with experimental results to verify the accuracy of the proposed model
This paper presents the effect of dynamic air-gap eccentricity on
the performance of a salient-pole synchronous machine. The modified
winding function approach (MWFA) accounting for all space harmonics has
been used for the calculations of machine winding inductances. In
addition, the winding inductances have been calculated by the
finite-element method to support those calculated by the MWFA.
Relationships between stator-current-induced harmonics and dynamic
air-gap eccentricity were investigated. The coupled magnetic circuits
approach has been used for modeling the synchronous machine performance
under the dynamic air-gap eccentricity. Finally, experimental results to
substantiate the theoretical findings are presented
A cageless reluctance motor having nonsinusoidal space
distributions is analyzed. Inductance variations of several cageless
reluctance-synchronous machines for high-speed drives were measured.
Based on the results of the measurements, the direct and quadrature-axis
inductances are predicted using derived expressions. In addition, these
are also predicted by the conventional method and compared with the
machine parameters obtained by the load tests. The inductance equations
were used in the measurement of parameters of the test machines, and
their validities were experimentally confirmed. The proposed method is
found to predict accurate unsaturated machine parameters